Tree and Shrub Diseases


Treatment Programs are specific to conditions that are causing decline to the trees and shrubs on your property.  Treatments are designed to meet longevity, tree specie and fit in with the personal preferences of our customers.

The majority of tree diseases are caused by fungi that are weather related.  Protective treatments work well to retard fungus development.  Control methods range from Foliar Spray to Trunk Injections and include good cultural practices.  Fungus diseases can affect the roots, leaves and needles, trunks and vascular systems of trees and shrubs.

Tree vigor is most important when treating fungus problems.  Fertilization and preventative methods of control are most affective in protecting your valuable plants.  Tree selection is a priority when creating a landscape that will be disease free.

Arbortech can help you to keep your property healthy and beautiful.


Secondary problems, which can be insect infestations, disease pathogens or pathological decline, are all the result of a primary condition.

The soil environment that is home for your tree must exhibit mineral, organic matter, water and air in adequate proportions.  Any lack of one or more of these properties can and most likely will result in the invasion of a secondary decline.

Insect pests and disease pathogens are opportunistic and recognize when it serves them best to attack.

Soil compaction has been found to be a number one contender in the primary decline category.  Compaction is nearly always the result of a man made action, but also can be the result of naturally occurring conditions, such as heavy pounding rain. 

Driveways which border trees, pedestrian walkways, landscape projects which require heavy equipment are just a few of the reasons soils can become compacted.

Arbortech has the experience to recognize this most damaging condition and the ability to correct it with the most modern equipment available.  Air Spades are most valuable when addressing soil compaction problems.

Feeding and Aeration stations will help eliminate tree failure and secondary problems from damaging your trees and shrubs.

Hydro-aeration is another valuable tool when dealing with hard packed soils and allows both fertilizers and organic material such as Mycorrhizae to be introduced at the same time.

Arbortech has diagnostic tools available to determine exactly which method of aeration is best for your trees and shrubs.


Plant vigor is essential for maintaining landscape trees and shrubs.  The stress of urban and suburban landscapes usually comes from the lack of natural resources which nourish trees. When leaf debris is removed, your plants source of food goes with it.  The loss of these natural nutrients leaves an open door for a loss of vigor resulting in tree decline as both insect and disease pathogens recognize weakness and know when to attack.

An appropriate invigoration program must take into account tree age and specie, existing soil conditions, current tree health, location and what specific nutrients are most needed.

Both Spring and Fall Soil Amendments are most valuable, especially in our changing environment.

Knowing whether or not to fertilize a sick tree is most important.  Some fertilization products can increase insect populations, while other fertilizers can aide in the development of fungal spores and disease.

Mycorrhizae and other organic bio-stimulants, such a Sea-Kelp have proven themselves to be very affective for plant invigoration.


What is Verticillium Wilt?

VerticilliumWilt Infected Tree

Verticillium is a fungal disease of many species of trees, shrubs and crops.  As described in its name Verticillium Wilt causes a distinct wilting, browning and curling of leaves, which is usually its first visual indication your trees or shrubs have a problem.  Verticillium fungus in short will foul or block the xylem vascular tissues of the host plant, thus causing a reduction of water and nutrients to the crown or foliage of the plant.

Verticillium can kill a plant quickly or in many cases can be a slow declining type of death.  Some symptoms reveal yellowing of leaves, defoliation, stunted growth and discoration of the stem tissue when a pruning cut is made.  If the host plant should succumb to Verticillium, the area in which that host lived will be infected with the inoculates of the disease.  These inoculates will remain in the soil environment for long periods of time and can infect new trees or shrubs planted in this area if the new host is of a susceptible specie.  The disease can also be spread by root to root contract, from one tree to another.  Pruning from a disease tree to a healthy tree can occur, if pruning tools are not sterilized between cuts.  This persistent disease is spread thru airborne means.  Some insect pests can also act as vectors to transmit this disease.

How can Verticillium be controlled?

Plant disease resistant varieties.  Do not plant non-resistant varieties in areas where this disease was previously present.  Sterilize pruning tools between cuts.  Keep tree and shrubs vigor up thru fertilization.  There are various Trunk Injections that may be valuable in suppressing the spread of this fungus.  They should be applied after determining the degree of infection in the host tree.  Arbortech can help you make the decision as to whether to treat or not.  Some susceptible tree specie are Maple, BoxElder, Horse Chestnut, Ohio Buckeye, ServiceBerry, Boxwood, Northern and Southern Catalpa, Camphor tree, YellowWood, Dogwood, Smoke  tree, Quince, Russian Olive, Ash, Kentucky Coffee, English Walnut, Golden Rain tree, Tulip, Osage Orange, Magnolia, Black Gum, Cork, Pin Oak, Red Oak, Black Locust, Japanese Pagoda, Linden and various Elm species.  Some resistant or immune species are Sycamore, Alder, Birch, Hop Hornbeam, Hickory, Pecan, Chinese Chestnut, Hackberry, Hawthorne, Beech, Honey Locust, Holly, Walnut, Butternut, Larch, White Oak, Willow Oak, Willow and Zelkova trees.


What is Fireblight?

800px-Apple tree with fire blight

Fireblight is a bacterial infection that can become prominent in wet weather conditions in the early spring.  This bacterium can cause the death of buds, leaves, flowers and new growth.  The decline from fireblight in our area is usually found on Crabapple, Callery Pear, Cotoneaster, Spirea, Mountain Ash and Quince. 

How can I tell if my trees have Fireblight?

The most obvious visual symptom of Fireblight is when leaves become shriveled and black, as if scorched by fire.  

What can be done to help trees suffering from Fireblight?

Over nitrogen fertilization can stimulate the development of Fireblight* Plant resistant species* There are chemical spray applications available as well as Trunk Injection products that provide control if applied in a timely fashion by and experienced licensed applicator* Arbortech is very skilled in treating trees infected with Fireblight.

There are many varieties of trees that are resistant to Fireblight that are easily found in local nurseries.  Arbortech can gladly provide you with a list of these trees upon request.

rhododendron clip image004


What is Phomopsis Twig blight?

Phomosis is another fungal disease that is moisture related.  Overwatering, poor site drainage and wet spring weather are all contributors to this damaging disease.  Phomopsis loves to attack Juniper, Taxus, Arborvitae, Fir, Hemlock and Larch among others.

How will I know if my plants have Phomopsis?

Usually the first signs are the dying back and browning of branch tips.  Foliage can become faded and reddish brown.  The black fruiting bodies of these fungal spores can be found at the base of diseased and dead needles.  This fungus prefers to attack young new tissue.  Usually the darker color, more mature tissue is not as vulnerable.

What can be done to avoid and control this disease?

Plant species that are resistant to this problem. Avoid over watering and make sure plants get appropriate sunlight.  Chemical sprays applications should be applied at proper times by a knowledgeable licensed pesticide applicator.  Arbortech can provide you with the expertise needed to achieve optimum results.  Plants that have been found to be resistant to Phomopsis include common Juniper (Juniperus communis hornibrookii),  Eastern Red Cedar (Juniperus virginiana),  Creeping Juniper (Juniperus horizontalis), Marcella, Chinese Juniper (Juniperus chinensis), Glauca Hetzii, Pfitzerana Aurea, Var. sergentii and Aurea Gold Coast.


What is Cytospora Canker?


Cytospora is a fungal disease that primarily affects Spruce trees, such as Blue, Norway and White Spruce.  This is a slow moving fungus that can continue to kill off branches in the host tree for years.  In most cases, the continued loss of branches lessens the tree’s aesthetic value and removal become inevitable. 

How will I know if my Spruce has Cytospora?

Cytospoa creates the formation of open wounds (cankers).  These open wounds ooze sap which can become white and crusty in appearance.  The developing wounds will girdle the branch that is involved.  The Cankers release spores that can blow, splash and drip onto other healthy branches that can become infected, spreading the disease.

What can I do to help my diseased Spruce tree?

First and most important, is to have your Spruce inspected by a professional who can diagnose the problem correctly.  Infected branches should be surgically pruned out.  Diseased branches and other fallen Spruce debris should be removed from the area as it will act as a form of inoculum and cause new and continued infection.  The infected debris contains fungal spores that are the primary source of re-infection.  Spruce trees growing too close to each other, stressed by low fertility or drought conditions are more susceptible than others.  Arbortech can help to prolong the life of your Spruces by putting them on a program of proper pruning, aeration and fertilization.


What is Leaf Scab/Apple Scab?

Apple scab

Scab is another weather related fungal disease.  This disease can occur year after year, causing trees to defoliate and become susceptible to secondary conditions such as insect invasion and other disease pathogens.  Leaf Scab in our area is commonly found on Apple trees, Pear, Mountain Ash, Crabapples and Quince. 

How will I know if Leaf Scab is on my trees?

In early spring, brown and green spots start to become noticeable on leaves.  As the disease develops leaves become discolored, brown and start to fall prematurely.  Crabapples that are primarily planted for aesthetic value showing brilliant spring blossoms and fruit become landscape eyesores. 

What can I do if my trees get Leaf Scab?

As with most fungal diseases try to plant resistant species* When planting popular trees such as Crabapple, be sure to buy one of the many varieties that show good resistance*  Rake up fallen and infected leaves* There are many chemical sprays that work well to control Leaf Scab.  Trunk Injections are also good control techniques for controlling this problem* Timing of treatments is essential when dealing with Leaf Scab.

Arbortech has a program and strategy specifically designed to keep your trees healthy and fungal free.  We can also steer you in the right direction when picking the most suitable choice of plant for your landscape.


What is Diplodia Tip Blight?


Scotch, Austrian, Mugho and Red Pines are the primary targets of this persistent weather related fungal disease.  As trees mature, Diplodia kills more and more new growth each year.  Like many other fungal diseases Diplodia lessens tree vigor, appearance and overall health, which is an invitation to secondary problems such as insect infestation. 

What are the signs and symptoms of Diplodia Tip Blight?

Moist, rainy, cool weather is optimum for the spread and development of this disease.  These patterns cause needles to turn brown and drop.  Continual over wintering persistence of this fungus can cause whole branches to die.

What can be done to address a Diplodia Tip Blight infection?

Plant susceptible species of Pines appropriately, leaving room for air circulation to aide in the drying process during wet rainy spring weather.  Remove infected fallen needles from area.  Prune off infected dead tissue when trees are dry to avoid spreading spores to other parts of the tree and other nearby susceptible trees.  Keep tree vigor up thru fertilization.  There are several fungicide treatments available that can be applied by means of Trunk Injection or Foliar spray applications.  Multiple spray applications are usually needed at appropriate times, all of which depend on prevailing weather conditions.   In most cases treatments are applied for several years in a row to achieve good results. Arbortech has had excellent success with treatments for Diplodia Tip Blight.


What is Armillaria Root Rot?

Armillaria mellea 041031w

Armillaria is a fungal disease that can attack a variety of tree species.  The fungus loves old rotten tree stumps and dead roots.  It has been the demise of many a beautiful big Oak or Maple.  Trees growing in close proximity to decaying stumps or other infected trees can become infected.  The loss of sound wood and structural roots caused by Armillaria can claim responsibility for tree failure in windy conditions or ice storms.

How will I know if my tree has Armillaria?

The symptoms and signs of this disease are often noticed by yellowing foliage and die-back on twigs and branches.  Armillaria can persist on larger trees for many years while smaller trees may fail within only a short time.  In many cases the presence of mushrooms at the base around the trunk or beneath the canopy is prominent.  Some areas of bark may separate form the tree revealing a white mat of living fungus called a mycelial fan.

How can this disease be addressed?

Plant vigor is most important in prolonging the life of trees that are infected and also as a preventative measure to help protect them.  Drought stress enhances the spread of this disease, so watering can be helpful.  There are some indications that treating the infected soil around trees with Armillaria, with good fungus spores, called Trichoderma may be helpful as the good fungus tends to eat up or feed on the bad fungus.  Arbortech can provide you with a plan to save your tree after inspection and diagnosis in confirmed.  Planting of resistant species is recommended.  Here a few you might like to consider:

Chinese Elm, Amelanchier, Bald Cypress, Crabapple, Japanese Pagoda, Holly Oak, Sycamore, Prunus (Almond, Plum & Cherry) Dawn Redwood, Hawthorne, Scotch and Austrian Pines.


What is Black Knot?

Black Knot

Black Knot is a serious disease in the US that affects many trees in the Prunus specie, Purple Plum, Cherry, Peach and Prune are among a few of its victims.

Smaller twigs and branches often die within a year of being infected.  Larger limbs may survive for several years, but sooner or later will become girdled by the fungus.  Eventually the entire tree may be come so seriously infected, it will fail, if affective control measures are not taken.

Where does Black Knot come from?

The Causual fungus (Apiosporina morbosa) is responsible for Black Knot outbreaks.  The fungus over winters on branches, twigs and in previously infected knots.  The fungus produces spores that are spread thru the air on windy days, splashing rains and can also be spread on contaminated pruning tools.

Asko spores that land on new succulent growth can germinate and cause infection to new areas of the same tree and nearby trees that are susceptible.

How can I protect my trees from Black Knot?

Pruning out infected knots will help if done properly.  Cut at least 2 – 4 inches below each knot and sterilize pruning tool between each cut.  Remove all resulting debris from property, bury or burn.  When purchasing nursery stock, examine closely for the presence of existing Black Knots.  Fungicide sprays can offer significant protection against this fungus if proper pruning and sanitation is not ignored.  Timing of all spray applications is essential.  Arbortech can provide a professional program to implement all of the above.


What is Anthracnose?

maple anthracnose

Anthracnose is a fungal disease that can affect both shade and ornamental trees.  Some of its victims can be Ash, Oak, Sycamore, Basswood, Black Walnut, birch, Tulip, Dogwood, Catalpa, Horse Chestnut, Hickory and Maple trees.  This fungus attacks the foliage and can re-infect year after year, resulting in a weakened tree which is susceptible to secondary problems such as insect infestations, Canker and Witches Broom.  In spring over wintering Anthracnose spores can be spread thru the air by wind and splashing rain.  If the weather is cool and moist these spores will germinate and affect newly formed tender leaf tissue.  This fungus has been quite devastating to Ash, White Oak, Maple and Sycamore trees in our area for many years.

How will I know if my trees have Anthracnose?

Evidence of the Anthracnose varies, depending on the tree specie being infected.  Homeowners usually notice it when leaves prematurely litter their lawn.  Leaves develop spots and blotches that can be black, brown, purple or tan in color and become shriveled and distorted. 

How can this disease be controlled?

Removal of fallen infected leaves from the site is most important as it acts as a form of inoculums which can affect the tree and other host trees again next year.  Keeping tree vigor up is valuable, by fertilizing and watering.  When planting, install resistant tree species.  Anthracnose resistant trees can include London Plane, Oriental Plant tree and Oaks in the Red Oak group.  Several control methods are available. Fungicide spray applications can be applied using a variety of specific application techniques.  Arbortech uses both Trunk Injection and various Foliar sprays, in addition to a tree invigoration and aeration program.



What is Slime Flux?

Slime Flux is a bacterial disease usually brought on by physiological stress factors.

Tree wounds, natural cracks and splits, insects, poor pruning practices, soil compaction and poor branch angles are just a few factors that can cause a Slime Flux reaction.

Once trees become involved with Slime Flux, they can attract insect pests such as worms maggots, flies and ants that will further weaken the tree.

What can be I do if I see this Slime Flux condition?

Try to eliminate the stress factors that maybe causing the tree to react.  Fluxing areas can be cleaned with rubbing alcohol or a bleach solution of one part bleach to nine parts water.  Have a professional address proper treatment directions.  Tree invigoration can help along with Surgical Bark Tracing techniques.

Arbortech can provide the best approach to controlling this problem.


800px-Scale and sooty mold on a Eucalyptus tree

What is Sooty Mold?

Sooty Mold is a fungus that grows on the secretions from plant exudates and insects such as Aphids, Whitefly, Scale and other sucking type insects.  Sooty Mold is mainly considered a cosmetic problem and does not damage plants unless allowed to become excessive.  It may cause yellowing of foliage and stunt the growth of the host plant.  The main visual indication of this fungus is a black powdery coating on plant foliage.  

How do I get rid of Sooty Mold?

Sooty Mold is easy to control.  Simply get rid of the insect pest and the Sooty Mold will go away.  Unfortunately, once this fungus is on the foliage it takes quite awhile to wash off.  There are several environmentally friendly systemic pesticides available that control the pests that create Sooty Mold.  Plants underneath a canopy of a larger tree will often be subject to repeated Sooty Mold problems as the honeydew from pests feeding on the overhanging larger trees will drip down and continue to affect under story plants.

Arbortech can solve your Sooty Mold problems by Foliar Sprays, Trunk Injections, Trunk Drenches or Soil Drenches.

SEIRIDIUM CANKER (seiridum unicorne)


What is Seiridium Canker?

Seiridium Canker is a cankerous fungal disease which can affect Leyland Cypress, Arborvitae, Bald Cypress, Arizona & Italian Cypress and Junipers, among others.

This disease can seriously damage and kill trees.  Seiridium Canker is brought on by stress, usually weather related, such as drought, winter desiccation and other physiologic problems.  The disease is vascular in nature and can spread quite rapidly if not treated.

How will I know if my trees have Seiridium Canker?


The first visual signs are flagging (dead brown branches) of foliage, usually quite obvious when looking at the entire tree from a distance.  Upon closer inspection a swollen area or canker can appear which sometimes oozes sap from the cracks that are created.  These open cracks are an open wound by which fungal spores can enter when wind spreads them.  On many occasions Leyland Cypress, Arborvitae and Junipers are planted in a row for privacy, the disease can spread thru out the entire row quickly.

What can I do if I see indications my trees are infected?

Surgical/sterilized pruning is a first and most important step.  Cutting away any infected tissue a few inches below the canker is most important.  Plant invigoration and hydration is very helpful in putting this disease in check.  

Arbortech can put your trees on a program that will save these infected plants if diagnosed early enough.


rhabdocline fungus

What is Rhabdocline?

Rhabdocline is a fungus that affects Douglas Fir only.  It has caused the demise of many a Christmas tree nursery and many beautiful landscapes with Douglas Fir trees.

How will I know if my Fir tree has Rhabdocline?

In late winter or early spring look for reddish brown splotches on the upper needle surface.  There is a distinct division between the diseased tissue and the surrounding healthy green tissue.  As with most fungal diseases, high humidity, rain, and heavy morning dew cause this infection to occur.  Early spring is the time when buds are opening and susceptible new growth become infected.

How can Rhabdocline be controlled?

Keep plant vigor up!

Remove and destroy heavily infected trees before bud break.  Prune and remove infected limbs and branches.  In early spring, Fungicide spray applications should start, when buds are just starting to break open.  Usually four spray applications are needed and must be applied in a timely fashion.  

Arbortech can treat your Fir trees and keep them healthy.

RUST (Gymnosporangium)

pic of rust fungus

What is a Rust Fungus?

There are (3) Rust fungi that can affect the trees in our area.  All these fungi have a symbiotic relationship to Eastern Red Cedar.  Without the Eastern Red Cedar, there would be no problem.  The spores from these fungi become wind-borne and travel from Cedar to host plant, which may include Apple, Pear, Hawthorne, Quince and Crabapple.  In spring, Galls which are known as Cedar Apples can be found on Eastern Red Cedar, become wet and yellow with gelatinous horn protrudes which spew the Rust spores thru out the neighborhood finding their way to your flowering and fruit producing trees.  These fungal disease spores infect the leaves and fruits of the host trees and will re-develop on the undersides of those leaves or fruit lesions and then are carried back to the Cedar trees by wind or rain, to start the cycle all over again.

How will I know if I have Rust on my trees?

rust fungus pic

Rust is easy to spot.  Small yellow to orange spots appear on leaf surfaces.  In many cases orange/yellow pustules called Aecia are produced and very visible.  Check out the pictures and compare them to your trees leaves.

How can I control Rust on my trees?

Plant trees that are resistant to Rust.  Don’t plant susceptible trees in the same area as Red Cedar.  Diseased trees can be treated with both Foliar sprays or Trunk Injections.  Arbortech has a program for your Rust problems.  Keep infected plant invigorated.



What is NeedleCast fungus?

NeedleCast disease is a fungal condition that prefers various species of Spruce trees, especially blue Spruce.  Although it may take awhile to kill your Spruce, it will most certainly make your tree so unsightly you won’t want to look at it anymore.

Healthy Spruce trees usually hold their needles for as long as 5 years.  Once Rhizosphaera attacks, infected trees can barely hold their needles for one year.

How will I know if my Spruce has NeedleCast?

NeedleCast usually starts to show up at the bottom of the tree first.  Defoliation and browning needles become evident.  Although needles become infected in May and June, symptoms are not visible until the fall.  As the fall season continues, more and more needles may turn purple or brown and start to drop.

How can NeedleCast be controlled?

Keep tree vigor up by fertilizing and mulching.  When removing dead or dying limbs, use sterile pruning tools.  Shearing or shaping infected trees may spread the disease.  Do not shear or shape when needles are wet as this also spreads the condition.

Fungicide spray applications work well if applied in a timely manner by a licensed applicator who knows what chemical to use and when to use it.  This is when Arbortech can help save your Spruces and keep them looking great.


bleeding-beech 512930

What is Phytophthora?

Phytophthora is a soil borne fungal disease.  The spores of this fungus love wet as well as oxygen deprived soil conditions.  Compacted soils tend to pool water which stimulates the germination of this fungus.  When infected water splashes onto cracks, crevices or wounded bark, it can enter thru these openings and find itself a suitable place to survive and wreak havoc.  This fungal disease causes a disruption in the flow of water to the crown of the tree.  Leaves can become abnormally small, become wilted, stunt shoot growth and cause lesions on the branches and trunk that ooze or bleed a red-brown liquid.

Phytophthora fungal species can affect American & European Beech, Cherry, Dogwood, several species of Maple, Oak, Willow and Walnut, including a variety of shrubs.  There are species of Phytophthora fungi that can damage shrubs as well, such as Boxwood, Rhododendron, Azalea, Andromeda, Mountain Laurel, Juniper and Yew.

What can I do if my trees get Phytophthora?

Too little as well as too much water is a contributing factor to this disease.  Try to manage a good soil balance.  Maintain a well drained site thru aeration.  Mulch or ground cover can prevent wounding of bark areas by reducing puddling.  There are several treatments available that include Fungicide Trunk Drenches, Soil Drenches and Trunk Injections that show promise in controlling this disease.  An Arborist who is keeping up with developing treatments is most valuable.

(Phytophthora Cactorum)

What is Crown Canker?

crown canker

Crown Canker is a fungal disease which affects Dogwood (Cornus Florida) and may kill the tree or make it weak and susceptible to other secondary declining factors such as opportunistic insect Borers.

Disease can originate from mechanical injury during transplanting, weed-wacking, mower injuries, etc.

How will I know if my Dogwood has Crown Canker?


The symptoms and signs of this condition include:

* Reduced number and size of leaves
* Leaf color appears faded
* Foliage turns yellow and red in late summer and may prematurely defoliate
* Trees with Crown Canker may produce an abnormally large number of fruits         and flowers
* Leaves may appear to be curled, wilted or shriveled
* Top or crown starts to die and a Canker is usually present in the lower trunk
* On occasion this lower wounded area will ooze fluid

What can be done if my Dogwood has Crown Canker?

Surgical treatment of infected tissue will help.  Application of an anti-fungal dressing may also be of value.  Fertilization to boost vigor is most important.

If you Dogwood should fail, do not plant another Dogwood in the same area. Arbortech can best advise you as to which direction to consider.

© Chris Graham 2013